Control system for clothes drying machine



Feb. 11, 1958 E. G. OLTHUIS CONTROL SYSTEM FOR CLOTHES DRYING MACHINE Filed July 19, '1955 2 Sheets-Sheet l A wiils EUGENE C:- OLTHU l5 PIC-LE Feb. 11, 1958 E. e. OLTHUIS 2,822,625

CONTROL SYSTEM FOR CLOTHES DRYING MACHINE Filed July 19, 1955 2 Sheets-Sheet 2 FIG. 2. B 42 PIC-3.3

INVENTOR. EUGENE 6. OLTHU I5 56 "a zmmwy HIS ATTORNW United States Patent CONTROL SYSTEM FOR CLOTHES DRYING MACHINE Eugene G. Olthuis, Louisville, Ky., assignor to General Electric Company, a corporation of New York Application July 19, 1955, Serial No. 523,083

7 Claims. (Cl. 34-45) My invention relates to clothes drying machines and more particularly to electrical control systems for such machines.

It is an object of my invention to provide a new and improved electrical control system for a clothes dryer.

It is another object of my invention to provide an improved clothes dryer control system in which both the heating means and the drive motor of the dryer are controlled by a single temperature responsive switch.

A further object of my invention is to provide a new and improved temperature responsive switch particularly adapted for use in clothes dryers.

Still a further object of my invention is to provide a new and improved temperature responsive switch having a single temperature responsive element and including two contact operating positions and an intermediate off position.

In carrying out my invention, I provide a clothes dryer having heating means and a main drive motor. The heating means and the drive motor are controlled by an electrical control system including a single temperature responsive switch. To place the dryer in operation the switch is manually actuated whereby it energizes both the heating means and the drive motor. The dryer then operates to dry the wet clothes until a predetermined temperature condition occurs therein indicating that the clothes have substantially dried. The switch thereupon operates to de-energize the heating means and energize the drive motor only for a cool-down period of operation. When the dryer has cooled sufficiently, the switch then operates to its off position turning off the motor and terminating the dryer operation.

The features of my invention which I believe to be novel are pointed out with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, may be best understood by reference to the following description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a front elevational view of a clothes dryer including a preferred embodiment of my novel electrical control system, the view being partially broken away and partially sectionalized in order toshow details of the dryer;

Fig. 2 is a schematic showing of the single temperature responsive switch included in the control system, the switch being shown in its 0 position;

Fig. 3 is a view similar to Fig. 2 but showing the switch in one contact operating position thereof; and

Fig. 4 is a schematic showing of a preferred embodiment of the complete control system, with the temperature responsive switch being shown therein in its other contact operating position.

Referring now to Fig. 1, I have shown therein a domestic clothes dryer 1. The dryer 1 includes a wraparound cabinet structure 2 having a base 3 and a top 4. Within the cabinet 2 there is rotatably supported a drum or basket 5 in which the clothes are himbled during the drying operation. The basket 5 is mounted on a plurality 2,822,625 Patented Feb. 11, 1958 2. of flanged roller wheels 6 so as to be rotatable about a horizontal axis. Only the two wheels 6 at the front of the basket are shown in Fig. 1, but it will be understood that identical wheels are provided at the rear of the basket. The left-hand pair of roller Wheels 6 (as viewed in Fig. 1) are mounted on an idler shaft 7 and the righthand pair of wheels 6 are mounted on a drive shaft 8. During the operation of the machine the shaft 8 is driven from a main drive motor 9 (Fig. 4) by means of a belt 10 and a pulley 11. The resultant rotation of the righthand pair of wheels 6 causes the basket 5 to rotate at an appropriate speed to provide a tumbling action for any articles of clothing placed between the basket 5. Raised longitudinal ribs (not shown) may be provided on the inside surface of the outer cylindrical wall of the basket 5 in order to aid this tumbling action.

Articles of clothing may be placed within and removed from the tumbling basket 5 by means of a hinged door 12 provided in the front panel of the outer cabinet 2. The door 12 is positioned in front of a loading opening 13 defined in the front wall 14 of the basket, and when the door is opened, the machine operator may reach directly into the basket. The front wall 14 of the basket preferably includes a forwardly extending flange 15 around the edge of the opening 13 in order to prevent clothing from dropping down between the front of the basket and the front panel of the cabinet.

In order to extract moisture from the clothes, means are provided whereby warm air is blown through the basket 5 during the operation of the dryer. This air stream is set up by means of a suitable air-moving means such as the centrifugal blower 16 which is directly coupled to the drive motor 9. During the operation of the machine the blower 16 draws air into the cabinet 2 from the surrounding room. In the illustrated embodiment I have not provided any special air inlet openings in the cabinet 2 since it has been found that the sheet metal construction thereof provides a number of small air inlet openings at various points, such as at the junctions between the various overlapping panel sections. However, if desired, louvers or other additional air inlet openings may be provided in the side, front or rear walls or in the top of the cabinet. After entering the cabinet the air is drawn over a heater assembly including an electrical heating element 17 (Fig. 4) and then passes into the tumbling basket 5 through a plurality of perforations 18 in the rear wall 19 thereof. Although different positionings of the electrical heating means 17 may be used, it is preferably positioned behind the rear wall 19 of the basket. A preferred heater assembly and the mounting thereof is shown and described in my co-pending application S. N. 523,084 (now Patent No. 2,790,247), filed concurrently herewith and assigned to the same assignee.

The warm air entering through perforations 18 passes through the length of the basket 5 extracting moisture from the wet clothes being tumbled therein. At the front of the basket the moisture laden air is drawn through loading opening 13 into a basket discharge duct 20. This duct 20 is positioned between the front wall 14 of the basket and the front panel of the cabinet 2 and the air enters the duct through a plurality of apertures 21 in the rear wall thereof. The duct 20 leads to a suitable cyclone lint-trap structure 22 wherein any lint picked up from the clothes in the basket is separated from the discharge air stream. A preferred type of cyclone lint trap is disclosed and claimed in the co-pending application of Stephen L. McMillan S. N. 455,280, filed September 10, 1954, now Patent No. 2,813,353, and assigned to the same assignee as the present invention. From the lint trap 22 the discharge air is drawn through the blower 16 and then passed out of the dryer through a suitable discharge conduit (not shown).

In accordance with my invention the operation of the dryer 1 is controlled by an electrical control system including a single temperature responsive switch assembly 23. This switch. assembly 23 is preferably mounted in the dischargeduct directly in front of the basket openings 21. With this positioning the switch assembly 23 senses the temperature of the air immediately upon its leaving the basket. The air temperature at this point corresponds closely to the temperature of the clothes, and thereby the switch assembly 23 in effect senses the temperature of the clothes. This novel and advantageous arrangement of the temperature responsive switch with regard to the other elements of the dryer is described at length and claimed in my aforesaid application S. N. 523,084.

The thermo-responsive switch 23 controls both the drive motor circuit and the heater circuit of the dryer 1. For that purpose and as shown in Figs. 24, the switch includes a plurality of contacts 24, 25, 26, and 27. The contacts 24, 25, and 26 are mounted respectively on resilient contact arms 28, 29, and 30 fixed to a wall 31 of the switch housing 32. The remaining contact 27 is, however, mounted on the single contact operator 33 of the switch. This operator 33 comprises a column spring which is adapted to flex with snap action between two oppositely bowed positions. One of these positions is shown in Fig. 3 and the other in Fig. 4.

In order to operate the column spring 33 between the two oppositely bowed positions, there is provided within the switch 23 a single thermo-responsive element comprising the bimetal 34. The bimetal 34 is mounted in a wall 35 of the switch housing and at its inner edge is attached to one end of the column spring 33. The other end of the column spring is fixed in a notch 36 in the opposite wall 31 of the switch housing. The walls 31 and 35 are both formed of electrical insulating material so as to insulate the various components of the switch from each other and from ground. The remaining walls of the switch housing are formed of heat conducting material, for example sheet metal, so that the atmosphere within the housing assumes approximately the same temperature as the air in the surrounding duct 20.

To operate spring 33 the bimetal 34 bends in response to predetermined temperatures so that its inner end moves upwardly or downwardly (as viewed in Figs. 2-4). When the inner end of the bimetal 34 moves upwardly relative to the end attached to wall 35, it causes the column spring 33 to bow upwardly; conversely when the inner end of the bimetal moves downwardly, it causes the spring to bow downwardly. Referring to Fig. 3 it will be seen that, when the spring 33 is bowed upwardly, it closes the contacts 24, 25, and27. But when it is bowed downwardly as shown in Fig. 4, it closes the contacts 26 and 27. Besides these two contact closing positions, the spring 33 further includes an intermediate position. This intermediate position is shown in Fig. 2. In the intermediate position the spring 33 is engaged by means of a resilient latch member 37 which is mounted on an electrical insulator 38 secured to the bottom wall 39 of the housing 32. The latch member 37 extends through an aperture 40 in the column spring 33 and is provided at its end with an offset portion 41 which engages the upper surface of the column spring.

When the bimetal iscold, it tends to bend upwardly so as to carry the spring to its upwardly bowed position. and thereby when the bimetal is cold, it moves the spring into engagement with latch member 37. The latch member, however, prevents the spring from bowing or flexing beyond the position shown in Fig. 2 even though it is stressed to move further. The engagement between the offset portion 41 of the latch member and the upper surface of the spring securely holds the spring in the intermediate position. In this position the contacts are, of course, completely open so that no circuits can be completed through the switch.

Since the spring 33 when held in the intermediate position is stressed to move to its upwardly bowed position. it will be seen that, if the latch member 37 is released or disengaged from it, the spring will move to that upper position. In order to release the latch member 37 there is provided a movable actuating member or knob 42. The knob 42 is disposed outside of the switch housing and is connected to a stem 43 inside the housing by a connecting pin 44. The lower end of the stem 4-3 is provided with a conical recess, as shown, in order to control the latch member. The stem and the knob are mounted by a slide 45 which is slidably disposed within a bracket 46 attached to the upper wall 47 of the housing. The upper portion of the stem is threaded in a tapped bore in the slide, and thus by turning the knob 42 the portion of the stem relative to the housing and the latch member 37 may be varied. Specifically, turning the knob 42 adjusts the stem 43 axially toward or away from the latch member. The knob and the stem are spring biased upwardly (as view in Figs. 2-4) by a spring 48 disposed between the knob and the upper wall of the housing. A ledge 49 in the bracket 46 engages the slide 45 to determine its normal portion.

The knob 42 when pushed inwardly moves the stem 43 axially inward so that a side of the recess in the end of the stem engages the upright leg 5t} of the offset portion 41 of the latch member. Specifically, the right hand slope of the stem recess (as viewed in Figs. 24) engages the end of the upright leg 51 so as to bend the latch member to the left. This bending brings the offset portion 41 into alignment with the aperture 40 of the spring 33 and thereby releases the spring for movement to its upward bowed position. The spring being stressed by the cold bimetal to move in that direction immediately moves to that position. It will be noted that the upright leg it of the oifest portion 41 is in contact with the side or edge of the aperture 4%) when the spring is in its upper position. The latching member 37 thereby does not slip under the spring to latch it in its upper position. Rather, due to this contact between the leg 59 and the edge of the aperture 49 the offset portion 41 and the aperture are kept aligned so that the spring can move thereafter to its downwardly bowed position without substantial interference from the latch. The latch member cannot move under the spring so as to prevent this movement.

The upper position of the spring 33, that is its amount of flexure or bow in the upper position, is determined by means of the stem 43. When the spring is released from the latch, it bows upwardly until it strikes the lower end of the stern (as shown in Fig. 3). The stem then acts as a stop halting the movement of the spring. The position at which the spring is stopped may be varied by adjusting the normal position of the stem relative to the housing. The stem is preferably formed of electrical insulating material to prevent grounding of the circuits through the switch when it engages the latch member and the spring.

Referring now to Fig. 4, i will describe the manner in which the switch 23 is incorporated in my improved ryer control system. in my preferred system shown therein, the power for the dryer is supplied through the conductors 51, 52 and 53. The conductors 51 and 52 comprise a 226 volt supply, and the conductor 53 is an electrical neutral line, between which neutral and the conductor 51, there is a supply voltage of volts. In the illustrated system, the temperature-responsive switch 23 comprises the means whereby the respective circuits for the heater 17 and the motor 9 are connected across these supply conductors. When the push button 42 is actuated so as to release the latch 37, the spring 33 moves upwardly to the position of Fig. 3 closing the contacts 24. 25 and 27. This energizes both the heater 17 and the motor 9. The heater is energized with 220 volts across conductors 51 and 52 and the motor is energized with 110 volts across conductors 51 and 53.

The circuit for the motor 9 extends from the line 51 through a terminal 54 and the bimetal 34 to the spring 33 and the contact 27. From the contact 27 the circuit passes through the contact 25, the contact arm 29, and a conductor 55 to a door switch 56. The door switch 56 is connected directly to the main winding 57 of the motor and is connected to the start winding 58 of the motor through the contacts 59 of a motor centrifugal switch 69. The motor circuit is completed from windings 57 and 58 to the neutral line 53 through a common terminal 61 and a fusible safety link 62. The door switch 56 is closed by the door 12 whenever the door is shut, and is suitably spring biased so that it opens whenever the door is opened. The motor centrifugal switch 60 is operated by means of the motor 9 and closes the contacts 59 until such time as the motor comes up to speed. The contacts are then opened for normal motor operation.

When the spring 33 closes the contacts 25, 27, the motor 9 is put in operation by the above circuit so as to rotate the tumbling basket 5 and the blower 16. As a result, the clothes to be dried are tumbled within the basket and a stream of air is blown over them to extract moisture. It will be noted that, if the door 12 should be opened during the operation of the machine, the door switch 56 will immediately terminate the operation of the motor and thus the rotation of the basket and the blower. The heater circuit will also be opened by means of the centrifugal switch 69. If the motor should become overloaded, the fusible link 62 will melt and effect the same result.

The movement of the spring 33 to its upper position shown in Fig. 3 also results in the heating means 17 being energized. Specifically, as mentioned above, it results in the heating means being connected across the 220 volt supply conductors 51, 52. Starting at conductor 51 the circuit for heater 17 extends through terminal 54, bimetal 34, and spring 33 to the closed contacts 24, 25, and 27. From contact 24 the circuit continues to the heater through contact arm 28, a conductor 63, and a safety thermostat 64. The thermostat 64 is normally closed and opens only when a dangerous over-temperature condition occurs Within the machine. From the heater 17 the circuit is completed to line 52 through a conductor 65 and the contacts 66 of the motor centrifugal switch 60. These contacts are normally opened when the motor is idle. However, when the motor 9 comes up to speed, the centrifugal switch closes the contacts 66 at the same time that it opens the starting winding contacts 59. Since the motor 9 comes up to speed quite rapidly, this means that the circuit to the heater 17 is completed very shortly after the actuation of the push button 42 and the movement of the spring 33 to its upper position. The energization of the heater, of course, results in the air stream for the basket 5 being heated to a suitable temperature for extracting moisture from the colthes.

With both the heater 17 and the drive motor 9 energized, the dryer l is operative to dry the clothes placed in the basket 5. As the clothes are dried, the temperature within the basket 5 and thus the temperature of the outgoing air stream in the duct 20 rise slowly. For a period of the dryer operation the amount of heat supplied to the air and the clothes from the heating element 17 is approximately equal to the amount actually utilized for moisture extraction and during that period a temperature plateau may occur. The machine operates at this plateau or with a very slow rise until such time as the clothes are substantially dry. At that time the clothes and the discharge air in duct 20 begin to rise rapidly in temperature. Before this rapid rise occurs, i. e., during the normal operation of the dryer, the temperature in duct 20 is low enough that the bimetal 34 does not develop enough downward force to move the stressed spring 33 out of its upwardly bowed position. The contacts 24, 25 and 27 remain closed energizing both the heater 17 and the drive motor 9. However, when the clothes are substantially dry so that the temperature of the outgoing air rises rapidly, the bimetal develops enough downward force to overcome the force of the spring. Specifically, when a predetermined temperature of the air occurs indicating that the drying operation is substantially complete, the inner end of the bimetal 34 moves downwardly (as viewed in Figs 2-4) far enough to overcome the upward stress in that spring. This action of the bimetal causes the spring 33 to bow downwardly to its second contact operating position shown in Fig. 4. Since it is a column spring, the spring 33 flexes between its upper and lower positions with a snap action which is effective to break the heavy currents flowing through the contacts 24, 25, and 27.

When the spring 33 flexes to its lower position, this opens the contacts 24 and 25 and thereby de-energizes the heater 17. The flexing of the spring to the lower position, however, closes the contacts 26 and 27 and thereby continues the motor 9 in operation. The contact 26 is connected to the motor supply line 55 through the contact arm 30 so that the motor is energized through substantially the same circuit as before, with merely the contact 26 substituted for the contact 25. The operation of the motor without the heating element being energized provides a cool-down period for the machine. In other words, air is still blown through the basket and the clothes are still tumbled, but no heat is supplied thereto. As a result, the machine cools down to a safe temperature at which the housewife can open the door of the machine and take out the clothes.

When the temperature of the machine, i. e. the temperature in duct 20, falls to a predetermined level, the bimetal 34 develops enough upward force to cause the spring 33 to flex upwardly, the flexing or bowing occurring with a snap action. In other words the inner end of the bimetal bends upwardly far enough to cause the spring to bow upwardly again (as viewed in Figs. 2-4). However, due to the latch 37, the spring cannot again move to its uppermost position shown in Fig. 3. Rather as it moves upwardly, it is caught by the offset portion 41 of the latch and held in its intermediate position. In this intermediate position (Fig. 2) none of the contacts of the switch are closed and thereby the machine is completely de-energized. The motor circuit as well as the heater circuit is turned ofi so that operation of the dryer is completely terminated. The snap action of the spring is eflfective to break the motor circuit without any undesirable arcing.

From the above, it will be seen that in my new and improved electrical control system the operation of the dryer is controlled by a single temperature-responsive switch. This single switch contains but a single temperature-responsive element for effecting the control. The single temperature-responsive element combined with the action of the column spring provides a switching action effective to make and break both the heater and the motor circuits. The action of the switch provides for normal dryer operation, a cool down period and complete termination of dryer operation.

In my preferred system the control may be adjusted to change the dryer from normal operation to cool down at different machine temperatures. This is desirable since dissimilar types of fabrics require different drying times, whereby the temperature of the machine when the clothes are dry varies from fabric to fabric. The illustrated control may be adjusted for different fabric loads by rotating the knob 42. The knob 42 turns the stem 43 and since the stem 43 is threadably mounted, it thereby moves relative to the switch housing and spring 33. Since the stem 43 holds or stops the spring 33 in its upper heater energizing position (Fig. 3), this adjustment of the stem adjusts the amount of fiexure or how of the spring in that position. The amount of force required to move the spring from its upper position to its lower position depends upon this 7 fie irure of the spring. The more the spring-is flexed or bowed, the more force is required from the bimetal. Since the force produced by the birnetal is dependent upon the temperature to which it is subjected, the result is that the more the spring is flexed, the higher the machine temperature must be before the bimetal can operate the spring to its lower position (Fig. 4). Thus by rotating the knob 42 so that position of stem 43 is changed, the control may be adjusted for different types of fabrics.

The machine temperature at which the cool down operation is stopped and the dryer completeiy turned off is determined by the amount of fiexure or bow of the spring in its lower position. This ileX-ure is controlled by the stop 67 which is mounted on the bottom wall 39 of the switch housing by a suitable electrical insulator 68. The stop 67, in my preferred embodiment, is pre-set in position so that cool down is always terminated at the same temperature. However, it is obvious that stop 67 could be suitably arranged so as to be adjustable by the operator for termination of the cool down period at different temperatures.

It will be noted that my new and improved temperature responsive switch is very simple in design and thereby is easy to fabricate and assemble. It can be manufactured at a very low cost compared to dryer controls using a timer motor drive and sequence cams. Further, due to its small number of moving parts, adjustment and Wear problems are reduced to a minimum.

While in accordance with the patent statutes I have shown whatat present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from my invention, and I, therefore, aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A control system for a clothes dryer including electrical heating means and a drive motor, comprising a heater circuit, a motor circuit, and a single temperatureresponsive switch for controlling both of said circuits, said switch including a single temperature-responsive element and a single contact operator movable by said ele ment, said operator having a first position efiective to close both of said circuits, a second position effective to close said motor circuit only, and a third position eifective to open both of said circuits, a latch member normally retaining said contact operator in said third position and releasable to allow said contact operator to move to said first position to initiate dryer operation, said temperature responsive element being operative thereafter to terminate said operation when the clothes have dried, said element first moving said contact operator to said second position upon a predetermined temperature condition of said dryer thereby to provide a cooling period for said dryer, and then moving said contact operator to said third position to terminate dryer operation.

2. A control system for a clothes dryer including electrical heating means and a drive motor, comprising a heater circuit, a motor circuit, and a single temperatureresponsive switch for controlling both of said circuits, said switch including a single temperature responsive element and a contact operating spring movable by said element, said spring having two contact operating positions and being movable therebetween with snap action, said spring closing both of said circuits in one of said positions and said motor circuit only in the other of said positons, a latch member for holding said spring in an intermediate position between said contact operating positions, said spring opening both of 'said circuits when in said intermediate position, .and a control member for releasing said latch member to allow movement of said spring to said one position to initiate said dryer operation, said operation being terminated upon a predetermined teinperature condition of said dryer by said temperature re sponsive element moving said spring first to said other position to energize said motor circuit only for acool-- down period, and then after cooling of said dryer moving said spring back to said intermediate position to deenergize both of said circuits.

3. A control system for a clothes dryer including electrical heating means and a drive motor, comprising a heater circuit, a motor circuit, and a single temperature-- responsive switch for controlling both of said circuits, said switch including a single bimetal and a contact operating column spring movable by said bimetal, said spring having two contact operating positions and being. movable therebetween with snap action, said spring; closing both of said circuits in one of said positions and. said motor circuit only in the other of said positions, a resilient latch member for holding said spring in an intermediate position between said contact operating positions, said spring opening both of said circuits when in said inter-: mediate position, and a control knob for releasing said resilient latch member to allow movement of said spring to said one position to initiate dryer operation, said operation being terminated upon a predetermined tem-- perature condition of said dryer by said bimetal moving. said spring first to said other position to energize said motor circuit only for a cool-down period, and then after cooling of said dryer moving said spring back to said intermediate position to de-energize both of said circuits, said resilient latch member holding said spring in said intermediate position after its return thereto.

4. A temperature-responsive switch comprising a column spring having two oppositely bowed positions, a temperature-responsive element for moving said spring between said bowed positions, a plurality of contacts closed by said spring in each of said bowed positions, a latch member for releasa-bly retaining said spring in an intermediate position between said bowed positions, a control member for releasing said latch member to allow said spring to move to said one of said bowed positions, and said latch member being effective to reset to its spring retaining position upon subsequent movement of said spring to the other of said positions by said temperatureresponsive element.

5. A switch comprising a column spring having two oppositely bowed positions, a temperature-responsive element for moving said spring between said bowed positions, a plurality of contacts closed by said spring in each of said positions, a resilient latch member having an oifset portion for engaging said spring to retain said spring in intermediate position between said bowed position, a movable control member for bending said latch member to disengage said offset portion from said spring thereby to allow said spring to move to one of said bowed positions, said latch member resiliently returning to its spring engaging position on subsequent movement of said spring to the other of said bowed positions by said temperatureresponsive element whereby said spring is retained in said intermediate position when said temperature responsive element subsequently attempts to move said spring back to said one bowed position.

6. The combination of claim 5 wherein said spring engages said control member and is stopped thereby in said one position, said control member being adjustable relative to said spring to vary the bow of said spring in said one position thereby to vary the force required from said temperature-responsive element to move said spring to said other position.

7. A temperature responsive switch comprising a column spring having two oppositely bowed positions, a bimetal mounting one end of said spring for moving said spring between said bowed positions, a plurality of contacts closed by said spring in each of said bowed positions, said spring having an aperture therein, a resilient latch member extending through said aperture and having an ofiset portion for engaging said spring thereby releasably to retain said spring in an intermediate position between said bowed positions, a control member biased to a normal position and movable therefrom against said latch member to disengage said ofiset portion from said spring, said 5 spring flexing against the end of said control member when released from said latch member and being held thereby in said one position, said latch member being effective to return to its spring retaining position upon the subsequent movement of said spring to said other position 10 by said bimetal.

References Cited in the file of this patent UNITED STATES PATENTS Gorsuch Apr. 25, 1950 Rittenhouse et a1 Apr. 19, 1955 Harris et a1 Sept. 13, 1955 Brady Oct. 4, 1955 Hire May 21, 1957 

